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Kumar, Rohtash
- Petrography of Neogene Siwalik Sandstone of the Himalayan Foreland Basin, Garhwal Himalaya: Implications for Source-Area Tectonics and Climate
Authors
1 Sedimentology Group, Wadia Institute of Himalayan Geology, P.O. Box 74, Dehradun 248001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 55, No 1 (2000), Pagination: 1-15Abstract
The 1.6 km thick Neogene fluvial sandstone (Middle Siwalik; 9-5.23 Ma) in the Dehradun sub-basin (west central sector of Himalayan Foreland Basin) is characterised by distinct grey colour, and salt and pepper texture. They can be divided into poorly indurated (friable), Matrix-Rich Sandstone (MRS) and indurated (hard), Matrix-Poor Sandstone (MPS). The sandstone is classified as lithic arenite (Q55F5R40; Mx2; 50%), lithic graywacke (Q61F3R36Mx24 29%) and sublithic arenite (Q75F5R20 Mx3; 21%). The MRS is fine- to very fine-grained lithic graywacke, and the MPS is rnediurn to fine-grained lithic to sublilhic arenite.The framework composition of the sandstone points to its derivation from a provenance comprising sedimentary, low to medium grade metamorphic and igneous source rocks. Significant increase of metamorphic element above 750ml level (7.65 Ma) and particularly from 900m level (7.50 Ma) suggests a widespread erosion of the uplifted Himalayan gneiss or the Higher Himalayan Crystallines (HHC). The uplift of Higher Himalayan Crystalline was due to tectonic adjustment along the Main Central Thrust (MCT) between 7.65-7.50 Ma. Results of this study also suggest fluctuating semi-arid to semi-humid climate till 8.5 Ma. However, a distinct deviation from semi-arid to humid climatic phase is observed between 8.5 and 7.6 Ma.
Keywords
Sedimentology, Petrography, Himalayan Foreland Basin, Neogene, Sandstone, Siwalik, Dehradun.- Sedimentology of the Middle Siwalik Subgroup of Mohand Area, Dehra Dun Valley, India
Authors
1 Wadia Institute of Himalayan Geology, 33, General Mahadev Singh Road, Dehra Dun-248001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 34, No 6 (1989), Pagination: 597-616Abstract
The Middle Siwalik Subgroup of Mohand area (1800 m thick) is divided into three units: (1) sandstone-mudstone interval (340 m), (2) thickly bedded multi storied sandstone (1060 m), and (3) conglomerate-sandstone-mudstone interval (400 m). Three major facies are recognised, namely: conglomerate, sandstone, and mudstone facies. Sandstone is the dominant litho-facies and displays frequent erosional surfaces along which mud-clasts are present. The common sedimentary structure is trough and planar cross-stratification.
Palaeo-flow measurements of trough cross-stratification show prominent modes in SE and NW directions. However, planar cross-stratification shows a high order of deviation in mean vector azimuth from trough cross-stratification. The fining-up in grain-size from erosional surface (Se facies) to mudstone (Fm facies) through trough and planar cross-stratified sandstone (St-Sp facies) and ripple drift laminated sandstone (Sr facies) has been recognised.
The mudstone intervals are almost negligible, while mud-clasts and suspension load in the sandstone (channel facies) are high (to to 25%). The absence of mudstone unit in multi storied sandstone complex may be attributed to the extensive and frequent avulsion on the large braided alluvial fan. This study reveals that sedimentation pattern of multi storied complex is similar to that of modern radial fan of Kosi river.
- Magnetic Polarity Stratigraphy of the Siwalik Sequence of Haripur area (H.P), NW Himalaya
Authors
1 Palaeomagnetics Laboratory, Wadia Institute of Himalayan Geology, Dehradun-248001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 47, No 6 (1996), Pagination: 683-704Abstract
A 2375 m thick sequence consisting of sandstone-mudstone alterations was sampled for magnetic polarity stratigraphy in Somb Nadi and its tributary, Jamni-Khol in the Haripur area of Himachal Pradesh. 200 palaeomagnetic sampling sites were selected from 45 overbank intervals of fluvial cycles. Only fine-grained sediments were sampled to get the ideal results from stable single domain grains. Progressive thermal demagnetization was carried out at intervals of 25, 50 and/or 100°C. A considerably stable secondary remanant magnetization was removed above 450°C with the isolation of characteristic remnant magnetization component at 600°C. Corrected mean directions for the normal and the reversed sites are D = 349°, I= 28° and D = 168°, I= -28°, respectively. The Tatrot/Pinjor faunal event is recognised on the local magnetic polarity time scale at 2.6 Ma (1685 m level) and the Middle to Upper Siwalik transition (Dhok Pathan/Tatrot boundry) at 5.26 Ma (500 m level), approximately. Predominance of piedmont depositional system at around 3.2 Ma (1450 m level) suggests uplift and denudation of the Outer Leesser Himalaya during this period. First record of the Pre-Tertiary clast-dominated conglomerate is observed at 2.6 Ma and that of Tertiary clast-dominated conglomerate at 1.76 Ma. An average rate of sedimentation of 45 cm/1000 years was observed till 2.6 Ma. Further, it shows increasing and decreasing trend after 2.6 Ma with a maximum value of 54 cm/1000 years and a minimum of 8 cm/1000 years sediment accumulation.Keywords
Magnetic Polarity Stratigraphy, Geophysics, Siwalik, Himachal Pradesh.- Role of Tectono-Climatic Factors in the Neogene Himalayan Foreland Sediments: Petrology and Geochemical Approach, Kangra Sub-Basin
Authors
1 Sedimentology Group, Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN
2 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
3 Department of Geology, University of Pune, Ganeshkhind, Pune - 411 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 6 (2008), Pagination: 787-807Abstract
The Neogene Siwahk fluvial succession (12 77-4 48 Ma) of the NW Himalayan foreland basin, east of Ravi River, are deposited under varied Tectono-Climatic conditions. Petrography and geochemistry of the sediments were carried out to understand the relative roles of tectonics and climate in this basin.The sandstones are classified as sub-litharenites with subordinate arkosic-graywacke. The dental components particularly the rock fragments are consistent with the inferred source area presently disposed towards the north of the depocenter and suggest that the Higher, Lesser and Lower Tertiary formations supplied detntus since 12 77 Ma. The Th/Sc vs. Zr/Sc ratio indicates sediment recycling. The Cr and Ni, negative Eu anomaly, LREE enrichment and moderately flat HREE in the mudstones collectively suggest dominant contribution from felsic igneous rocks beside contribution from basic, sedimentary/metamorphic hithology. Near consistent nature of the dental modes and geochemical parameters through time suggest unvarying source since 12 77 Ma.The present study also infers that the source areas uplift owing to tectonic activity of Chad Thrust at least by 12 77 Ma with a perceptible activity of MBT after 8 Ma.
The 5180 variations in soil carbonates reveals ongoing intense monsoon system since 12 77 Ma followed by a phase of aridity at 91 Ma. Presence of fresh and weathered feldspar, limestone, basic volcamcs and mica, both in humid and arid phase indicate rapid deposition and preservation. Despite the climatic turnover from humid to arid, distinctive changes in the framework mineral compositions over time is not discernable.
The petrographic and geochemical data reveals that the near similar source area, relatively rapid transport, moderate chemical weathering and sediment recycling controlled the composition of the sediments of the HFB in response to tectonics and climate.
Keywords
Climate, Provenance, Tectonics, Himalayan Foreland Basin, Siwahk, Kangra.- Manifestation of Intra - Foreland Thrusting in the Neogene Himalayan Foreland Basin Fill
Authors
1 Wadia Institute of Himalayan Geology P. 0. Box 74, Dehra Dun - 248 001, Uttaranchal, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 59, No 6 (2002), Pagination: 547-560Abstract
Neogene basin fills of the Middle and Upper Siwalik Subgroup in the central sector of Indian foreland basin record changes in fluvial architecture, dispersal pattern and provenance in response to deformation and uplift of the frontal Himalaya. The 2.4 km thick Neogene Siwalik succession in the Subathu sub-basin exposed in the vicinity of Nahan Thyst (intra-foreland thrust or IFT) shows fine-to medium-grained grey sandstones of multi-storey, sheet type deposited by transverse trunk rivers. These sandstones are gradually replaced by fine- grained buff sandstone of ribbon type deposited by relatively small piedmont rivers. A significant change in sediment dispersal from SE to SW is observed at 5.5 Ma for grey sandstone and to SE around 4.8 Ma for buff sandstone. Both the sandstones are lithic arenites with dominance of sedimentary rock fragments in the buff sandstone. The filling pattern and occurrence of softsediment deformation structures, particularly between 4.8 and 2.6 Ma, indicate tectonically controlled re-organisation of drainage pattern and gradual change in source area from Lesser Himalayan to Sub-Himalayan regions. These changes after 4.8 Ma are mainly governed by intra-foreland thrust activity, which resulted in partitioning of foreland basin. Further, a significant overlap of Tertiary clast-bearing conglomerate with that of pre-Tertiary clast-bearing conglomerate at around 1.77 Ma shows a major reactivation along IFT.Keywords
Foreland Basin, Himachal Pradesh, Subathu Sub-Basin, Intra-Foreland Thrust, Magnetostratigraphy, Fluvial Architecture.- Magnetic Polarity Stratigraphy of the Upper Siwalik Subgroup, East of Chandigarh, Punjab Sub-Himalaya, India
Authors
1 Department of Geology, University of Delhi, Delhi 110 007, IN
2 Institute of Geosciences, Shizuoka University, Shizuoka 422, JP
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 25, No 1 (1984), Pagination: 45-55Abstract
An approximately 900m thick succession of pre-Pinjor (Tatrot) and Pinjor beds of the Upper Siwalik Subgroup is exposed in the Khetpurali section which lies to the east of Chandigarh. Samples collected from the mudstone interval from forty-nine fluvial cyclic units exhibit a stable detrital remanent magnetisation. The study of magnetic polarity of these samples reveals the presence of six normal and six reverse magnetozones. The Tatrot-Pinjor faunal boundary has been interpreted to approximately lie at the Gauss-Matuyama boundary. Based on this interpretation, the Olduvai Event in Matuyama reversed polarity epoch spans 160m of the middle part of the Pinjor Formation. The local Pliocene/Pleistocene boundary in this section is interpreted to lie 170m higher in the sequence with reference to the Tatrot-Pinjor faunal boundary.Changes in the fluvial domain in the post-Gauss Epoch are interpreted to reflect changes from 'meander belt' deposits to 'braided stream' deposits. The first appearance of conglomerates in the section has been interpreted to occur in the post-Olduvai time.
- Major Element Geochemical Variations in a Miocene-Pliocene Siwalik Paleosol Sequence: Implications to Soil Forming Processes in the Himalayan Foreland Basin
Authors
1 Wadia Institute of Himalayan Geology, 33, General Mahadeo Singh Road, Dehra Dun - 248 001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 73, No 6 (2009), Pagination: 759-772Abstract
Elemental mobility based on major element geochemistry from 58 horizons related to six paleosols profiles in a typical Miocene – Pliocene Siwalik fluvial sequence in the NW Himalaya has been reported here. The paleosols developed over felsic parent material of fine to medium grained sandstone indicate notable enrichment of sesquioxides (Al2O3 = 29% and Fe2O3 = 54%) depicting significant leaching and dissolution. The depletion of base cations (mean wt% of Na2O = 0.24; CaO = 0.51) and SiO2 (mean wt% = 63.6) in the pedogenic layers and its enrichment in the parental material (mean wt% of Na2O = 0.44; CaO = 1.3; SiO2 = 70.1) shows a good gradient of elemental mobility due to pedogenesis. Bivariate plots of the base ratios (Na2O/K2O, CaO/K2O, and MgO/K2O) vs. Al2O3 reveal independent distribution for parent material, pedogenic horizons and the incipient zone indicating the gradual addition/removal of immobile/mobile elements with varying pedogenesis. Discontinuous and segmented pattern of the geochemical parameters enables discrimination of multiple pedogenic episodes and recognition of soil welding processes in the multistorey composite paleosols. We also test the applicability of the geochemical climofunctions: the Mean Annual Precipitation (MAP) and Mean Annual Temperature (MAT); that demands more data for calibration in the Siwalik paleosols.Keywords
Siwaliks, Mio-Pliocene, Paleosols, Geochemistry, Climate, Himalaya.References
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- Evolution of Inter-Montane Kargil Basin (Oligo-Miocene), Ladakh Himalaya: A Sedimentological Approach
Authors
1 Wadia Institute of Himalayan Geology, Dehradun-248001, IN